Microwave and millimeter-wave technologies have been widely used for position sensing, such as described in Stezer et al., “Microwave position sensor with sub millimeter accuracy,” IEEE Trans. Microwave Theory and Techniques, vol. 47, pp. 2621-2624, December 1999. Microwave and millimeter techniques have also been used for precision noise measurement, such as described in Ivanov et al., “Microwave interferometry: Application to precision measurements and noise reduction techniques,” IEEE Trans. Ultrason., Ferroelect., Freq. Contr., vol. 45, pp. 1526-1536, November 1998. Likewise, microwave and millimeter-wave methods have been applied to displacement measurement, such as described in Kim et al., “On the development of a multifunction millimeter-wave sensor for displacement sensing and low-velocity measurement,” IEEE Trans. Microwave Theory and Techniques, vol. 52, pp 2503-2512, November 2004.
In addition, microwave and millimeter technologies have been applied to cardio pulmonary sensing, such as described in Droitcour et al., “Range correlation and I/Q performance benefits in single-chip silicon Doppler radars for noncontact cardiopulmonary monitoring,” IEEE Trans. Microwave Theory and Techniques, vol. 52, pp. 838-848, March 2004. The mechanism of most of the microwave displacement-related measurement systems is the detection of the phase shift caused by the movement of the target. Based on this, a Doppler radar has been developed to monitor periodic vital sign movements, and a linear approximation was used to analyze the performance as shown by Droitcour et al. However, the system could only detect the frequency of movement, not the amplitude.
Accordingly, there is a need for a method and apparatus for accurate non-contact measurement of frequency and amplitude of mechanical vibration.